Caster for furniture



CASTER FOR FURNITURE Edison Dick, Lake Forest, Ill.

Application October 25, 1955, Serial No. 542,687

2 Claims. (Cl. 16-24) This invention relates to an article of furnitureand its relates more particularly to a leg construction in an article offurniture or equipment which is adapted to be moved about from place toplace for purposes of cleaning, use, placement, or repair.

For various reasons well known to man, various articles of furniture andequipment are moved about over a supporting surface from place to place.In the home or oiiice, articles of furniture such as chairs, sofas,beds, tables or the like are moved about a room and in and out of a roomfor giving access to the underlying surface for cleaning, for clearingthe room of the articles of furniture for decorating, for removal of thefurniture or equipment for repair, or for shifting the furniture orequipment for use or other reasons. In the retail establishment, sucharticles of furniture are moved about for similar reasons, and in theplant articles of furniture and equipment are moved from place to placefor use as well as for many of the reasons pointed out.

The frequency of movement and the extent of movement places a demandupon the energy of the person, depending upon the weight of the articleof furniture or equipment and the surface over which the article is tobe moved. Not infrequently, the article of furniture or equipment is ofa weight or size which cannot be easily handled by the housewife orother single person, with the result that the article of furniture orequipment becomes unavailable for use or else placement thereof mustawait the presence of more than one person or special equipment beforeit can be shifted from one place to another. y

This infiexibility in operation and use and the demand for manpower andtime is, of course, undesirable, and it is therefore an` object of thisinvention to produce an improvement in the structure of a leg supportingsuch furniture, equipment and the like which enables the article offurniture and equipment to be moved easily and efficiently over thesupporting surface Without the demand for labor, without the need tolift the piece of furniture or equipment off of its supporting surface,Without limitation because of the weight or size of the piece offurniture or equipment, and without interfering with the stability ofthe piece of furniture or equipment in use, and without detracting fromthe utility ofthe piece of furniture or equipment for its intended use.

The improvement embodying the features of this invention resides in theconstruction of the legsV with a hollow end portion having a roller inthe form of a sphere shiftable into and out of the end portion of eachof the legs between a normally extending position into engagement withthe supporting surface and a retracted position. When in extendedposition, the roller projects outwardly from the end portion of the leginto rolling contact, with the, supporting surface so that the articleof furniture or equipment can be shifted about in any direction Withoutetfort. When in retracted position, the roller is displaced whollywithin the open end portion States Patent Tice of the leg so that thearticle of furniture or equipment is supported by the leg itself incontact with the supporting surface, thereby to provide a sturdy supportwhich resists lateral displacement when in use.

In practice, the roller is adapted normally to be located in theextended position in rolling contact with the supporting surface toenable movement of the article of furniture or equipment. However, whenin use, as when occupied by a person or the like, the added weight isadapted to be sufficient automatically to displace the roller fromextended to retracted position so that rolling Contact is replaced bythe desired steady support which is provided when the leg itself engagesthe surface for support of the chair, other article of furniture, orequipment.

Retractable rollers have heretofore been suggested for use in the endportions of supporting legs for furniture or equipment, but they havenot been adopted commercially because of the complex nature of thecontemplated structures or because of the inilexibility in adapting thestructure for universal use with pieces of furniture or equipment ofdifferent dimensions, weight, or for use on different types of surfacesor for a number of other reasons, including the inability to provide forcontinuous or periodic use, the inability to eifect repair orreplacement of parts in a simple and efficient manner, and the inabilityto maintain the rollers in satisfactory condition for operation.

Thus it is a further object of this invention to produce a leg structureof the type described and to provide an improved roller attachment foruse in same which is replaceable or else can be repaired in a simple andetlicient manner and which is flexible in operation for use withstructures of various dimensions and weights and which operates smoothlywhether used periodically or continuously.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, an embodiment of the invention is shown in the accompanyingdrawing, in which- Figure l is a perspective elevational View of a chairembodying the features of this invention;

Figure 2 is a sectional elevational view of the end portion of the chairshown in Figure 1;

Figure 3 is a sectional view taken along the line 3-3 of Figure 2; and

Figure 4 is a sectional view of a portion of the leg structure shown inFigure 2, embodying a modification in the construction thereof.

escription herein will be made of the practice of this invention` in theleg structure of a chair, but it will be understood that the concepts ofthis invention in an improved leg structure can be adapted as Well toother pieces of furniture or equipment supported on legs, and which aremoved from place to place over a supporting surface.

Referring now to the drawing, l0 represents a chair or other article offurniture or equipment having a seat l2, a back 14, and legs 16depending from the underside of the seat into engagement with thesupporting surface.

In accordance with the practice of this invention, the lower end portionof each of the legs 16 is provided with an opening 18 extending upwardlyfrom the end for a substantial distance into the leg for receiving anadaptor 20 in the form of a rigid, cup-shaped housing 22 formed of sheetmetal or the like material and mounted' in fitting relationV within theopening liti to prevent inadvertent endwise displacement of the housing22 from the leg. The opening in the leg may be of rectangular shape orof other polygonal shape but it is preferred to form the leg, or atleast the end portion thereof, of a tubular member such as of a tubingformed of aluminum, stainless steel, or the like having a bore extendingtherethrough which is of uniform dimension. The crosssectional dimensionand shape of the housing 22 will correspond to the opening 1S so as toenable a fitting relationship to be established upon insertion of thehousing 22 into the opening to prevent relative endwise or erosswisemovements.

Mounted within the housing 22 for endwise sliding movement is a block 24formed of bearing material or other material having a low coefficient offriction. A spherically-shaped groove 26 is formed in the center of theunderside of the block for purposes of receiving a roller 2S in the formof a steel ball or the like in seating relation therein. The bearingblock 24 is dimensioned to have a cross-section corresponding in shapeand dimension to the opening or bore 30 through the housing to enablefree sliding movement yof the bearing block in guiding relation endwisebetween the walls of the housing. When the desired fitting relationshipis provided, the walls ot the block bear in sliding relation against thewalls of the housing to prevent collapse, while the legs of the chairengage the outer walls of the housing all around to support the housingand maintain the desired interiitting `and assembled relation.

The top end of the housing is closed by the wall 32 to form the housinginto a cylindrical cup-shaped member, and the portion of the housingdefining the open end at the bottom is formed With a ilange 34 extendinginwardly into the path of the bearing block 24 to engage the undersideand prevent displacement of the bearing block from the housing. Thebearing block is constantly urged in the direction toward the open endinto engagement with the inturned ilanges 34 by resilient means, such asa coil spring 36, having one end bearing against the underside of thetop wall 32 while the other end bears against the top wall of thebearing block 24. The coil spring is tensioned within the openingexisting between the bearing block and the wall 32 to provide a forceurging the bearing block towards its normal position into engagementwith the flange 34 sufficient to overcome the load normally supported bythe leg 16 but insufficient to overcome the load existing when an addedWeight is supplied, as in normal use `of the chair or other piece offurniture or equipment.

Thus, when the housing 22 is inserted as a unit into the end of the legwith the ilanged open end of the housing at the lower edge of the leg,the spherical roller 28 supported in the bearing block 24 will normallyextend outwardly beyond the end of the leg into rolling engagement withthe supporting surface when the bearing block is displaced endwise bythe coil spring 36 into engagement with the flange 34, while the chairis not in use. Thus the chair or other piece of furniture or equipmentcan be moved easily on its rollers in any direction over the surface.When, however, the load is increased in use, the proportional load addedto each leglwill be suihcient to overcome the force exerted by thesprings, thereby to cause the bearing block to be displaced upwardlywithin the housing until the end of the leg 16 cornes into engagementwith the surface t0 support the load, thereby to inactivate the rollerand prevent further rolling movement of the chair over the surface untilthe added load is removed to enable the elements to return to theirnormal position.

The improvement embodying the features of this invention resides furtherin the construction of the roller in an assembly which can be formedinto a unit separate and apart from the chair legs to enable insertionor removal as a unit into and out of the open end ofthe chair leg .foruse. Thus the units can be assembled inthe most ellicient manner andinserted in position ofuse or re- 4 moved for replacement or repairwithout diiculty and without the necessity for special equipment orlabor.

For this purpose, the end portion of the cup-shaped housing is formedwith a plurality of circumferentially spaced apart slots which subdividethe lower end portion of the housing into separated sections. The coilspring 36, which is the first to be inserted into the housing inassembly, is dimensioned to have a normal length, when extended, whichis greater than the distance remaining between the top wall 32 and theupper surface of the bearing block 24 when the latter is in its normalextended position so that the bearing block will be constantly urged bythe spring towards its extended position with the desired force. Thestrength of the coil spring 36 can be preselected for counterbalancingthe calculated weight expected normally to be supported by theparticular leg. After the spring 36 has been inserted, the bearing block24 is inserted and then alternate sections 34a on the ends of thecup-shaped housing are turned inwardly substantially perpendicularly toform the stop flange 34 for engaging the bearing block to preventdisplacement beyond the extended position. The intervening sections 38are turned outwardly substantially perpendicularly from the walls of thehousing for engaging the end 40 of the leg when the housing is insertedin position of use into the opening 18, thereby positively to locate thehousing in the leg with the end of the housing aligned with the end ofthe leg.

The bearing block 24 may be molded of a plastic material having a lowcoefficient of friction, such as polyethylene, polystyrene,polymethylmethacrylate, and the like, or a graphite composition orbearing metal or the like. The bearing block may be molded into aunitary structure which is dimensioned to be inserted into the open endof the cup-shaped housing prior to bending 0f the sections to form thestop flanges. When formed of a single piece of bearing material, thespherical groove adapted to receive the roller is preferably formed to ahemispherical shape or Ias close to a hemisphere as possible but nogreater, otherwise the spherical ball cannot be inserted or replacedwithout destroying the bearing.

When the groove 26 is formed to hemispherical shape or less, thespherical roller cannot be held in .the groove by the bearing. Undersuch circumstances, the flanges 34 turned inwardly from the lower endportion of the cup-shaped housing should be dimensioned to provide aspaced relation between `diametrically disposed edges which is slightlyless than the diameter of the spherical roller so that the inturnedflanges will operate to permit the roller to extend outwardly from thehousing, yet prevent the spherical roller from falling out of thehousmg.

It is preferred to form the bearing block 24 of two or more sections 24aand 24b separable along radial lines so that the groove may be formed toprovide a spherical section which is slightly greater than a hemisphere(about when the sections are iltted together. Thus the block can belitted together with the roller prelocated within the groove that isformed to provide a self-supporting assembly which can be inserted as aunit into the open end of the cup-shaped housing to be retained thereinby the llanges 34 which are subsequently provided. The close fittingrelationship of the bearing block with the inner walls of the housingprevent separation of the pieces so that the spherical roller is held bythe block in position of use 4during movement endwise between extendedand retracted positions of adjustment.

It will be apparent from -the foregoing that the ro1ler,`

the bearing block, and the spring may be assembled into the housing inthe manner described to provide an adaptor for use with various piecesof furniture. It is only necessary. to select an adaptor for size andweight and then insert the adaptor into the opening provided in the endof thechair leg. To avoid scratches to the floor or other pieces offurniture, a foot 42 formed'of rubber or other cushioning material isdimensioned to be slipped over the end of the chair leg after theadaptor has been inserted. The bottom wall 44 of the foot is providedwith a central opening 46 which is dimensioned to enable the sphericalball to extend therethrough into rolling contact with the supportingsurface when the bearing block is displaced to its extended position.When in retracted position, the lower wall 44 of the foot 42 engages thesupporting surface in a manner to prevent inadvertent displacement.

By way of modification, means may be provided for adjustment of thetension of the coil spring 36 to provide the described balance betweenload and force to adapt the unit for a range of loads, thereby to extendthe range of use per unit and to decrease the amount of inventoryrequired by suppliers thereof. For this purpose, a slideable disc plate50 is provided in the housing 22 for shifting movement endwise in theupper end portion thereof. The spaced relationship between disc plate 50and the top wall 32 of the housing is adapted to be adjusted by means ofa set screw 52 which extends through an opening 54 in the ytop wall ofthe housing into engagement with the plate 50. The top wall of thehousing is threaded about the opening for receiving the threaded shankof the set screw 52 so that the end portion of the set screw can beadjusted endwise in the housing by turning movement of the head 56 inone direction or the other. The head is accessible from the outside ofthe housing. Thus the tension of the spring 36 bearing against ytheplate 50 can be adjusted. The plate 50 can be adjusted prior toinsertion of the adaptor into position of use. If the desired balance isnot achieved, or in the event that the unit should become unbalanced inuse, the force available from the coil spring may be adjusted merely byremoving the unit as a whole frorn`the opening in the chair and thenadjusting the coil spring by means of the set screw to increase ordecrease the tension thereof, after which the adjusted unit can then bereinserted into the opening for use.

While description herein is made of a chair having the adaptor on allfour legs, it will be understood that the adaptor may be employed onlyon the two front legs, or the two back legs so that the chair can betipped onto the rollers for movement from place to place. In this eventthe force urging the spherical rollers to extended position would besuilicient to support the weight of the chair but insufcient to supportthe weight with a person sitting in the chair. In the preferredassembly, the legs are formed of tubular members such as the aluminumtubing which is used in the manufacture of modern kitchen or dinettesets with straight legs having open ends.

It will be further understood -that other similar means may be employedfor adjusting the slideable plate endwise within the housing and it willbe still further understood that other changes may be made in Ithedetails of construction, arrangement and operation without departingfrom the spirit of the invention, especially as defined in the followingclaims.

I claim:

1. In a caster, the combination comprising a housing having acylindrical side wall and an end wall extending across one end thereof,a split cylindrical block slidable longitudinally in said housing andhaving a spherically curved cavity in one end thereof, a spherical ballslidably rotatable in said cavity, said block being made of antifrictionmaterial, said cavity being substantially less than fully spherical inextent but substantially greater than hemispherical in extent to retainsaid ball in said cavity with said ball projecting out of one end ofsaid block to a substantial extent, said block being splitlongitudinally into two complementary identical parts to provide forinsertion of said ball into said cavity, said housing retaining saidparts of said block together with said ball therebetween, a springcompressed between said end Wall of said housing and said block on theend thereof opposite from said ball for biasing said ball outwardly ofsaid housing, and flange means turned inwardly on said housing from saidside wall at the end thereof opposite from said end wall for retainingsaid block in said housing, said ball normally projecting from saidhousing beyond said ange means but being movable into said housingagainst the resilient resistance of said spring.

2. In a caster, the combination comprising a housing having acylindrical side wall and an end wall extending across one end thereof,a split cylindrical block slidable longitudinally in said housing andhaving a spherically curved cavity in one end thereof, a spherical ballslidably rotatable in said cavity, said block being made of antifrictionmaterial, said cavity being substantially less than fully spherical inextent 'out substantially greater than hemispherical in extent to retainsaid ball in said cavity with said ball projecting out of one end ofsaid block to a substantial extent, said block being splitlongitudinally into two complementary identical parts to provide forinsertion of said ball into said cavity, said housing retaining saidparts of said block together with said ball therebetween, a springcompressed between said end wall of said housing and said block on theend thereof opposite from said ball for biasing said ball outwardly ofsaid housing, a plurality of angularly spaced inwardly extending flangeelements turned inwardly on said housing from said side wall at the endthereof opposite from said end wall for retaining said block in saidhousing, said ball normally projecting from said housing beyond saidflange elements but being movable into said housing against theresilient resistance of said spring, and a plurality of outwardlyextending ange elements turned outwardly from said side wall on saidhousing and interspersed angularly between said inwardly extendingflange elements.

References Cited in the le of this patent UNITED STATES PATENTS 984,457Wilkerson Feb. 14, 1911 1,944,185 Langer Jan. 23, 1934 2,613,389 CramerOct. 14, 1952 2,707,301 Urso May 3, 1955 FOREIGN PATENTS 177,751 CanadaJune 19, 1917

